Effects of female body size on lifetime fecundity of Monochamus urussovii (Coleoptera: Cerambycidae)

To analyze the relationship between female body size and lifetime fecundity (LF) in Monochamus urussovii (Fischer), 17 pairs of adults were reared on Picea jezoensis (Sieb. et Zucc.) Carrière twig sections and were allowed to oviposit on Abies sachalinensis (Fr. Schmidt) Masters bolts at 25 °C and 16:8 h light:dark. The means of life span and LF were 42.5 days and 28.2 eggs for fertile and sterile females combined, respectively. The mean lengths of preoviposition and oviposition periods (OPs) of fertile females were 12.1 and 28.1 days, respectively. The potential fecundity was estimated to be 72.1. Path analysis showed that female body size, i.e., mass and elytral length, had positive effects on LF through the oviposition rate but not through the OP. Ovariole number was 24 and did not vary according to body size, indicating a higher egg productivity per ovariole in large females than in small ones. Higher egg productivity per ovariole in large females is true for each of three other synovigenic lamiine beetles with an almost fixed number of ovarioles. The body size-dependent egg productivity per ovariole is considered to be one of the reasons for the body size–LF correlation in synovigenic species with a fixed ovariole number.